In the field of threaded fasteners, a wide range of configurations is known and is currently available. In general, threaded fasteners comprise a shank portion upon which one or more thread leads are formed. The thread leads create or define a helical inclined plane along which the fastener threads contact or engage surface portions of an object or substrate into or out from which the threaded fastener is to be inserted or removed as the threaded fastener is rotated in either the clockwise or counterclockwise direction. Various threaded fastener designs, including the formation of the thread leads thereon, have been specifically developed for use within different substrate materials, such as, for example, wood, metal, composite materials, concrete, and the like. In connection with most threaded fasteners, a head is formed upon one end of the shank portion so as to facilitate the rotation of the threaded fastener into and out of the substrate material, an insertion tip portion is formed upon the opposite end of the shank portion, and the thread lead is formed upon the shank portion between the head and tip portions of the fastener. The particular structural characteristics or features of the thread lead determine both the torque insertion and torque withdrawal properties of the threaded fastener, as well as the pull-out resistance properties of the threaded fastener once the fastener is threadedly disposed within the substrate material.
In connection with the fabrication of most conventional threaded fasteners, the thread lead is uniform in shape throughout the entire axial extent of the fastener shank portion, however, specialty fasteners have been developed which have incorporated a variety of different structural features upon the thread lead. For example, threaded fasteners having ridges or depressions along the thread lead have been developed so as to be specifically capable of penetrating certain substrate materials. For the most part, however, these designs have compromised flexibility with respect to being used in connection with diverse applications, and in addition, optimal performance during usage has likewise been adversely affected.
A need therefore exists in the art for a new and improved threaded fastener, which can be adapted for specific purposes and substrate materials, through means of unique structural features integrally incorporated within the thread lead, wherein the driving or insertion torque required to rotate the threaded fastener in connection with the rotational driving and axial insertion of the same into an underlying substrate is substantially uniform or constant, and sufficiently reduced so as not to exceed the torsional strength characteristics of the material from which the threaded fastener is fabricated whereby the threaded fastener will be permitted to be inserted within the underlying substrate to its fully required or desired penetration depth without experiencing any fracture or separation of the driven head portion of the threaded fastener, and wherein further, the threaded fastener can be manufactured in a relatively simple and economical manner.